automem - smart pointers for D

Unlike the C++ variants, the smart pointers themselves allocate the memory for the objects they contain.
That ensures the right allocator is used to dispose of the memory as well.

Allocators are template arguments instead of using theAllocator so
that these smart pointers can be used in @nogc code. However, they
will default to typeof(theAllocator) for simplicity. The examples
above will be explicit.

Another reason to have to pass in the type of allocator is to decide how it is to
be stored. Stateless allocators can be "stored" by value and imply zero-cost Unique pointers.
Singleton allocators such as Mallocator (that have an instance attribute/member function)
don't need to be passed in to the constructor. This is detected at compile-time as an example
of design by instrospection.